It is known to preserve wine in wine bottles by evacuating the air space above the liquid once some of the wine has been consumed, and then sealing this evacuated space. European Patent specification EP-B-0234607 describes one method and apparatus by which this can be accomplished. In that specification, a special stopper is placed in the bottle neck. This stopper has a slit in it which acts as a non-return valve in that it opens if a vacuum is created above the stopper, to allow air to be sucked out of the bottle, but closes again as soon as the external pressure is greater than the pressure inside the bottle. To create a vacuum above the stopper, a manual suction pump is used. This operates satisfactorily, but pump operation is time-consuming and strenuous if an adequate level of vacuum is to be produced in the bottle. There is also no convenient or accurate method of determining when a suitable vacuum level has been achieved.
It is also known from U.S. Pat. No. 4,684,033 to preserve wine in an opened wine bottle by inflating a bladder inside the bottle to fill the space above the liquid and to prevent oxygen from reaching the wine. To do this is a time-consuming operation which requires considerable manual dexterity in introducing the uninflated bladder into the bottle, and also requires the bladder to be washed and cleaned after each use.
It is also desirable to preserve sparkling wine, but if this is done by creating a vacuum above the liquid, then the sparkling character of the wine will be entirely lost.